Vicia villosa lectin-adherent Lyt-1+ spleen cells, obtained 4 days after immunization with an optimally immunogenic dose (0.5 microgram of Type III pneumococcal polysaccharide (SSS-III), increased the magnitude of the antibody response of mice to SSS- III upon transfer to recipients also immunized with the same antigen; however, the ability to demonstrate such enhancement depended greatly upon when such cells were transferred relative to immunization of recipients. Lectin-adherent cells augmented the antibody response of athymic nude (nu/nu) mice to SSS-III, and abrogated the expression--but not the induction--of low-dose immunological paralysis, a form of unresponsiveness mediated by suppressor T cells. These finds are consistent with effects usually attributed to the action of amplifier, rather than contrasuppressor, T cells.